The dielectric dispersion of the transparent relaxor ferroelectric ceramics PLZT 8/65/35 and 9.5/65/35 was determined in a wide frequency range including the microwave and infrared range. The number of observed polar phonons in infrared spectra gives evidence about the locally broken cubic symmetry and the presence of polar nanoclusters in the whole investigated temperature range up to 530 K. A single broad and symmetric dispersion that occurs below the polar phonon frequencies was fitted with the Cole-Cole formula and a uniform distribution of Debye relaxations. On decreasing temperature, the distribution of relaxation times becomes extremely broad which indicates increasing correlation among the clusters. The mean relaxation time diverges according to the Vogel-Fulcher law with the same freezing temperature 230±5 K for both ceramics, but different activation energies 1370 K and 1040 K for the 8/65/35 and 9.5/65/35 sample, respectively. The shortest relaxation time is about 10-12 s and remains almost temperature independent. Below room temperature, the loss spectra become essentially frequency independent and the permittivity increases linearly with decreasing logarithm of frequency. The slope of this dependence is proportional to T  4 in the investigated temperature range (above 210 K) which indicates appreciable anharmonicity of the potential for polarization fluctuations.

PACS: 71.20.Ps; 79.60.BmThe paper presents the X-ray photoelectron spectra (XPS) of the valence band and core levels of the semiconductive Bi 2 S 3 single crystal, which shows anomalies in various physical properties and weak phase transitions without change of symmetry. The XPS were measured with monochromatized Al K a radiation in the energy range 0-1400 eV and the temperature range 160-460 K. The valence band is located 0.55-6.5 eV below the Fermi level and shows non-linear dependence on temperature. Experimental energies of the valence band and core levels are compared with the results of theoretical ab initio calculations of the molecular model of the Bi 2 S 3 crystal. The chemical shifts in the Bi 2 S 3 crystal for the Bi and S states are obtained. Results revealed the origin of a weak polarity of the crystals at room temperature, which results in anomalies in the physical properties, and shifts the Fermi level and all the electronic spectrum.

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The paper presents the X-ray photoelectron spectra (XPS) of the valence band (VB) and of the principal core levels from the (110) and (001) planes for the ferroelectric semiconductor SbSI single crystal in the temperature range 215-390 K. The excitation source was Al Kα monochromatic radiation (1486.6 eV). XPS were analysed in the energy range 0-1400 eV. Experimentally obtained energies were compared with the results of theoretical ab initio calculations of surface and bulk atoms in the paraelectric and ferroelectric phases. The structure of VB is calculated and confirmed experimentally. Large shifts (3-5 eV) in the core-level binding energies of surface atoms relative to bulk atoms have been observed. They show a dramatic dependence on the surface crystallographic plane. This is the first observation of XPS shifts of that magnitude in solids. Influence of the phase transition on VB and core levels is studied and the mechanism of the XPS shifts in SbSI crystals is discussed.

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